Licht wissen 17 LED: The Light of the Future

Lightemitting diodes are the shooting stars of lighting. Tiny and extremely efficient, they are revolutionizing the world of light – delivering a whole new quality of lighting, addressing an ever growing number of applications and saving a great deal of energy. LEDs are the light of the future and are conquering the realm of general lighting.

licht.wissen 17

LED: The Light of the Future

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.all-about-light.de

01

The LED heralds a new age of lighting – it beats every other option hands down Its wide scope for application, its flexibility in terms of shape and colour dynamics, its outstanding ef- ficiency and longevity make it the lighting tool of the future

LEDs address both indoor and outdoor applications, making for a new quality of lighting in offices, foyers and homes, on facades and fabrics, in streets and automobiles The possibility

of fine-tuning colour and light temperature to suit the time of day and meet particular ments makes LED light an everyday tool in hotels and shops, museums and theatres, indus- try and trade, and at the workplace Variable LED light is used by doctors to optimise a wide range of examinations, sets a dramatic and brilliantly colourful stage for concerts and TV shows and permits problem-free presentation of sensitive merchandise in infrared- and UV- free light

require-All these fascinating applications are addressed with extremely high efficiency and longevity Anyone who opts for LEDs gets green technology that is easy on the budget Containing no mercury, economical on power and virtually maintenance free, every LED makes a contribu- tion to environmental protection Where conventional lighting is replaced by LEDs with intelli- gent lighting management, the energy required for lighting is reduced by around 70 percent This makes for massive carbon savings and provides an incentive for all sides to help vigor- ously drive forward the further development and implementation of LED technology

In Germany, the Federal Ministry of Education and Research (BMBF) promotes LED ogy in a variety of ways as part of the country’s “High-Tech Strategy” Alongside basic re- search projects, it has launched an LED lead market initiative and introduced a competition under the banner “Municipalities in New Light” The lead market initiative, which draws on the expertise of the leading actors of the lighting industry, is designed to bring together partners

technol-to establish LED in general lighting and carry forward the new business models required The aim of the competition is to promote the use of LED by paying tribute to the top ten munici- pal demonstration projects

People do not buy what they do not know, so it is essential to get more information about the new technology into the public domain This booklet will help do just that Highlighting the unique advantages and applications of LEDs, it shows the scope for design and presents ideas for improving our “light climate”

The spectrum of information is rounded off by articles looking at the way LEDs work, the lighting management options they offer and the technical applications they can address – as well as real-life examples of LEDs in use These insights into the new technology will broaden our perspective of the world of lighting and pave the way for new and original ideas for the light of the future

Read this booklet and discover new worlds of light!

Editorial

Andreas Kletschke

Assistant Ministerial Counsellor

Federal Ministry of Education and Research

Introduction LED: The Light of the Future 06

Facade and Advertising 12

Office and Administration 14

Shops and Presentation 32

Emergency and Safety Lighting 48

Modules, Systems, Quality Features 22

Operating Devices and Ballasts 40

Safety, Marks of Conformity, Standards 50

OLED – Technology of the Future 54

FAQs about the Light-Emitting Diode 56

Contents

[02] LED spots set the stage for the organiccurves of the concrete walls With a lightingmanagement system, mood images can beproduced in RGB colours

02

Whether indoors or out, decorative or tional – LEDs (light-emitting diodes) permitsolutions today that would have been in-conceivable even a few years ago Startingout as a coloured signal indicator, the en-ergy-efficient semiconductors advancedrapidly to become one of the principal lightsources for accent and orientation lighting.

func-With white light and intelligent ment, LEDs now ensure a high quality oflighting right across the range of outdoorand indoor applications

manage-LED technology is regarded as the mostimportant invention in the history of lightingsince Edison’s development of the “lightbulb” over a hundred years ago Never be-fore has so much light come from such asmall fitting; never before have light sourcesworked so reliably for so many years andconsumed so little electricity Even recently,

attention still focused on the richness ofcolour achieved by LEDs; today, high-per-formance LEDs are transfiguring generallighting

The many positive characteristics of thelight-emitting diode include:

> extremely long life and virtual freedomfrom maintenance

> high efficiency

> white and coloured light with good colourrendering properties

> insensitivity to vibration

> light with almost no heat generation, no

IR or UV radiation, no interference with nocturnal insects

> instant, flicker-free lighting that is infinitelydimmable

> very compact design

> no mercury content and no end-of-lifedisposal problems

LED: The Light of the Future

Light-emitting diodes are the shooting stars of lighting Tiny and extremely efficient, they are revolutionizing the world of light – delivering a whole new quality of lighting, addressing an ever growing number of applications and saving a great deal of energy LEDs are the light of the future and are conquering the realm of general lighting

03

LEDs are long-lived and efficient

LEDs have an operating life of 50,000 hours

or more That amounts to six years of

main-tained operation or 45 years of light for

three hours a day So they can be installed,

connected and then forgotten – because

no matter how intensively they are used, it

will be a long time before any maintenance

work is required

LEDs burn fifty times longer than

incandes-cent lamps And are far more efficient

than many conventional light sources: their

luminous efficacy is much higher and their

directional light can be easily and efficiently

bundled An 8W LED lamp, for example,

delivers the same amount of light as a 60W

incandescent lamp Today, LED systems

can even stand comparison with

fluores-cent lamps And their potential is far from

exhausted yet: LED luminous efficacy in the

past has doubled about every two years

LEDs for a “green future”

Even today, the longevity, efficiency and

high lighting quality of LEDs literally make

conventional lamps look old by comparison

The days of “energy-guzzling” light sources

like the incandescent lamp – generating

[05] Street lighting is an area with high tential for savings Local authorities could re-duce their energy consumption by as much

po-as 70 percent With LED luminaires, it is evenpossible to achieve a saving of 80 percent

At present, however, LEDs are not yet an timal alternative for every lighting application

op-[03] The city at night: highly focused LEDlight is ideal for highlighting architectural details

[04] Innovative LED technology enhancesthe gastronomic experience Discreet spotsprovide glare-free light at the table

04

05

[06] LEDs are the light source of the future.

The table below shows the lighting industry’s

ten-year forecast for lamps and their

applica-tions

cent of global energy consumption for ing could be saved through the use of LEDs.And that is a great deal of energy – because

light-no less than a fifth of the electricity ated in the world is used for artificial lighting

gener-The German government is also focusing

on the tiny diodes as a source of able solutions It has sponsored many LEDresearch projects in recent years under thebanner of Germany’s “High-Tech Strategy”.Now, its sights are set on harnessing thewealth of expertise in the German lightingindustry to translate LED solutions swiftlyinto practical products At the beginning of

sustain-2009, the Federal Ministry of Education andResearch teamed up with partners in indus-try and science to launch the “LED LeadMarket Initiative” Its purpose is to acceler-ate the introduction of LED technology on

2009 – transposed into German law as theEnergy Using Products Act (EBPG) – set thedirection; inefficient products are being re-moved from the market The old Edisonlamp is one of the light sources set to bephased out across the European Union; thelist also includes a number of inefficienthalogen lamps, fluorescent lamps and high-pressure mercury lamps

The solution for the future is LED Eventoday, experts estimate that up to 30 per-

Solutions tailored to needs and good

for the environment

LEDs are highly efficient light sources But

they offer even greater savings potential

when used in combination with “intelligent”

lighting management systems designed for

daylight- and presence-dependent

regula-tion The dynamic duo achieves savings of

up to 80 percent in offices, shops and

street lighting – with a corresponding

re-duction of carbon emissions

But LED solutions are more than just easy

on the environment and the pocket No

other light source has ever offered so much

scope for design in terms of form and

colour LEDs can be integrated practically

anywhere Their rich colours add an

emo-tional dimension and offer maximum lighting

quality for human needs: LED lighting

con-cepts allow light to be optimally tailored to

meet human biological requirements – from

cool bright light for concentration to a

soothing lighting atmosphere that facilitates

relaxation in the evening

So LEDs are not just an increasingly

popu-lar option for accent and event lighting;

they are also advancing on the general

lighting front But for LED systems to play

out their many advantages, the quality

needs to be right The development and

manufacture of efficient LEDs require a

great deal of expertise – something which

does not go into every product found on

the market Consumers are well advised to

rely on the experience of reputable

manu-facturers

Even today, the cost of a quality system is

quickly recouped through high efficiency,

longevity and convincing lighting quality

And system performance is improving fast

LED development is advancing just as

rap-idly as computer and flat-screen technology

High performers: LEDs in corridor lighting

High lighting quality and efficient technology are compelling arguments in favour of LED solutions forgeneral lighting As the example here shows, higher capital outlay is quickly recouped The comparison isbased on downlights in a 20 metre long corridor, fitted with 2x26W fluorescent lamps in one case and 26WLEDs in the other The calculation is based on 10 years of operation with a burning time of 12 hours a day,

250 days a year, and an electricity price of 21 ct/kWh

LED Fluorescent lamp

Germany’s lawmakers have given local authorities a new responsibility; they wantthem to set a good example in terms of energy conservation At the same time, theidea is to sharpen city profiles in globalcompetition Lighting and the face of thecity at night play a significant role in this.

They heighten appeal, shape image, vide security – and offer massive potentialfor savings The German Electrical andElectronic Manufacturers’ Association(ZVEI) estimates that a switch to efficientsolutions could save around € 400 million

pro-a yepro-ar in street lighting pro-alone

After all, more than a third of street lighting

is over 30 years old Obsolete technology isresponsible for low coefficients of utilisation:

inefficient lamps such as high-pressuremercury vapour lamps – which will bebanned in the EU in 2015 – consume toomuch energy LED luminaires are not justmore efficient; they also have other winningfeatures:

> homogeneous light

> long life and low maintenance

> precise optical control, preventing sirable stray light

unde-> simple dimming and lighting ment

manage-Tailored white light

White light is now available in just about anyhue required and can be selected to suitthe type of street in question: warm whitelight with a colour temperature in the2,700–3,000 kelvin range is right for the at-mosphere of a historical town centre, park

or residential area; LED luminaires ing neutral white light are appropriate forbusy roads and business parks – and veryefficient at 70 lumen/watt

produc-Many municipalities are already switching toLED luminaires In the Lower Saxon town ofSoltau, for example, old twin-lamp mush-room luminaires fitted with 80W high-pres-sure mercury vapour lamps were replaced

by LED street lights with single 59W LEDmodules The result: the LED solution re-duces the energy required by 60 percent.This is due not just to its higher efficiencybut also to integrated lenses permitting pre-cise light control even without secondaryoptics

[10] Ground-breaking: flat recessed spots

and a narrow recessed ground luminaire with

blue LED light guide visitors safely to the

building

[11] The light of the recessed ground

lumi-naires with LEDs sets distinctive accents in

the pedestrian precinct

[12] The LED luminaires cast agreeably

white light evenly over footpath and road

The power required for each light point is just

34W and the LED modules can simply be

replaced as required

LEDs for City and Street

LEDs have been used in decorative outdoor lighting for years With white light, they now also make for optimal visual conditions on roads and paths No other lighting technology couples so much freedom for lighting design with such low energy and maintenance requirements

10

Light that meets needs

Electronic regulators integrated in the

lumi-naires themselves make for very high

effi-ciency: they ensure that light output is

auto-matically kept constant throughout the LED

luminaire’s life of around 50,000 hours and

that illuminance never falls below the

mini-mum level required These regulators alone

cut energy requirements and costs by 15

percent

Lighting control also enables LEDs to be

automatically dimmed in the event that no

or only little light is required When the

sen-sors register the presence of pedestrians,

cyclists or automobiles, the lighting can be

specifically powered up again to illuminate a

particular street section LED systems can

easily be incorporated in lighting or

tele-management systems Modular concepts

facilitate system maintenance and make it

easier to replace LED modules at the end of

their service life

Even though it may be tempting, switching

from old luminaires to LED solutions or

re-placing defective lamps with LED retrofit

systems is still problematical Lighting and

electrical values need to be checked and

approved by manufacturers and operators

12

11

1514

[13] High-impact facade lighting: NarrowLED light strip is used here as an indirect lightsource to accentuate the sheet aluminium fa-cade

[14] The lettering and the globe on the roof

of Hamburg’s Atlantic Hotel are visible from agreat distance The colour of the LED lightcan easily be varied as required The light-emitting diode’s long life saves energy andexpensive maintenance work in placeswhere access is difficult

[15] An attention-grabber: The multimediafacade of Vienna’s Stadion Center shoppingmall can be used to display static or movingimages The entire facade is enveloped in aflexible, 80-metre long LED net offering at-tractive possibilities for outdoor advertising.Each of the 37,620 LEDs is individually con-trolled by a video management system

[16] LED spots with a highly focused beamdirect the eye to historical details

Their light seems to come from nowhere yet has a remarkable presence: in compactdesigns and with RGB colour controllers,LEDs provide striking accents on any scale

They also offer huge scope for lighting sign: narrow LED strip winds around bendsand corners, lends emphasis to window reveals and arches Up- and downlightsflood facades with homogeneous glancinglight that picks out structures in sharp relief Powerful floodlights with over a hun-dred high-performance LEDs effortlesslycast light to the tops of spires 240 metresabove the ground And extremely preciselighting effects are achieved by minimalistspots with extremely sharp contours

de-LED systems combine scope for designwith high efficiency and a long service life

Today, the large-scale floodlighting that waspopular in the past is also being increas-ingly replaced by low-key lighting accentsrealised by LEDs positioned directly on orclose to the facade This saves even moreenergy and reduces unwanted light emis-sions that might disturb local residents

Light advertising and “talking walls”

Intense colours and robust design long agowon LEDs a place in light advertising andcorporate colour branding Flexible, com-pact LED modules can easily be deployed

to illuminate individual characters or entirelogos – whether they are three metres high

or just a few centimetres Thanks to theirlow design height, LEDs integrate harmo-niously into the architecture and are a rec-ommended solution for backlightingtranslucent surfaces

With the necessary controllers, LEDs create

“talking walls” Media facades are in vogue;

they permit moving images at the push of

a button and attract lots of attention tising messages, news, light art or even

Adver-video recordings of events can thus be jected onto facades and walls

pro-In contrast to fluorescent lamps, specialLED modules make maintained, ignition-problem-free operation possible down totemperatures of minus 20° C – withoutcompromising on constant light, brilliantcolour saturation and low power consump-tion Another advantage: the longevity ofLEDs eliminates the need for regular lampreplacement and expensive maintenancework, especially at height, where luminairesare difficult to reach

LEDs for Facades From discreet integrated light strip to large-scale illumination, white or coloured LED light heightens the visual impact of architecture and grabs attention

16

[17– 21] Lighting atmosphere based on

requirements and time of day: the hybrid

luminaire for the conference room combines

direct LED light with energy-efficient T5

fluo-rescent lamps for indirect lighting Separate

switching and dimming for the two light

sources offers high lighting comfort

[19] Recessed LED modules make for a

friendly reception in the lobby

A uniform lighting level of 500 lux out the office? Those days are gone Light-ing concepts today are no longer static but flexibly adaptable to personal needs:

through-they ensure balanced, tailored lighting ateach workplace, they adjust to suit the time

of day and they send the right signals to the human biological clock This promotes

a sense of wellbeing in employees and enhances their peformance

LED systems not only achieve a betterquality of lighting Their high efficiency andlong life also make them a long term

“green” solution And scope for ment in that respect is still present in abun-dance in small and large offices: anyonewho refurbishes inefficient old installationsand switches to innovative technology withlighting management can save up to 75percent of the cost of electricity required forlighting And since lighting accounts fornearly 40 percent of all the electricity costs

improve-in an office buildimprove-ing today, the improve-initial improve-ment is generally recouped within just a few years through lower energy consump-tion

invest-LEDs at the workplace

Workplace lighting needs to meet high ergonomic and economic requirements

Quality office luminaires offer glare-free

lighting for optimal visual comfort even atcomputer workstations They conform tothe relevant standards and are energy effi-cient

New hybrid luminaires offer the best of bothworlds in one system: they combine ad-vanced LED technology, for example, withenergy-efficient T5 fluorescent lamps (16

mm lamp diameter) – a mix that makes forextremely efficient direct/indirect luminaires.They ensure that the punctual light of theLEDs is focused and directed onto the worksurface while the light of the fluorescentlamps radiates widely and evenly over theceiling

Hybrid luminaires thus offer cool direct LEDlight for optimal colour rendering – and with

a high blue content for biological stimulation– as well as warm indirect light for a sense

of harmony The possibility to switch anddim the LEDs and fluorescent lamps sepa-rately makes for tailored lighting comfort

A wide variety of lighting atmospheres canthus be created – finely tuned to suit per-sonal preferences and the nature of thework tasks performed The combinationalso ensures excellent quality of lighting inconference rooms

Apart from hybrid luminaires, there are alsopendant, recessed and standalone lumi-

LEDs for Office and Administration

Good workplace lighting motivates, promotes health and boosts performance Intelligent LED solutions meet these high requirements, fulfil statutory energy-saving regulations and make for a sustainable reduction of costs

1817

20 21

19

22

naires on the market that work exclusively

with LEDs And companies are starting to

switch over entirely to diode technology,

using high-performance LEDs to provide all

the lighting required for workplaces and

meeting rooms, foyers and corridors

Em-ployees’ and visitors’ footsteps are guided

by extremely flat modules that fit seamlessly

into the architecture At workplaces,

stand-alone or pendant luminaires with both direct

and indirect lighting components deliver

the glare-free 500 lux required

Better lighting, lower costs

The use of innovative LED solutions raises

lighting quality while at the same time

permitting a sustainable reduction of

light-ing costs Savlight-ings potential is maximised

by “intelligent” luminaire management,

whereby the brightness of each luminaire is

adjusted automatically in response to

pres-ence and daylight sensors So the artificial

lighting provided is no more than is actually

needed This is not only a practical solution

for offices The combination of LED

[22] LEDs provide all the lighting requiredfor this modern office building in Hamburg’sHafencity General and accent lighting on six floors is delivered by a total of 3,000 LEDluminaires

[23] High intensity and high efficiency: LED ceiling luminaires with acrylic glass diffu-sor for the aisle zone The recessed lumi-naires are only a few millimetres high and radiate light downwards in a wide uniformbeam

[24] At the workplace, standalone naires with direct and indirect lighting com-ponents guarantee glare-free, standard-compliant lighting Integrated presence- anddaylight-dependent control makes for maximum efficiency

lumi-[25] LED downlights lead the way to the lift

[26] The suspended hybrid luminaires eachfeature twelve 3W LED modules and two54W T16 fluorescent lamps Their reduceddesign harmonizes perfectly with the officefurnishings

naires and lighting management also saves

a great deal of lighting energy – and thuscosts – in corridors, seminar rooms, toiletfacilities and technical rooms

LED luminaires producing coloured orcolour-changing light set striking accents inreception areas, corridors and stairwells

Colour and dynamism emphasize areaswith a prestigious character and also en-liven meetings With a wide spectrum ofcolour temperatures, LEDs can even recre-ate the natural progression of daylight in-doors and thus promote relaxation and acti-vation in line with biological rhythms Andmaintenance? With LED solutions, that isnot an issue for many, many years

LEDs produce light – but that is about the only thing they have in common with halogen or energy-saving lamps Unlikeconventional lamps that work by heating afilament or by gas discharge, LEDs are tinyelectronic chips of special semiconductorcrystals

When a current is passed through the solidcrystal, it induces electroluminescence: thediode glows, emitting what is sometimesreferred to as “cold light” This is because,unlike the light of an incandescent lamp,LED light is not heat driven

With edges only around a millimetre long,LEDs are among the smallest light sourcesavailable – not much larger than a pencildot To protect them from environmental in-fluences, the semiconductor crystals areembedded in a plastic case, which helpsproduce higher light densities and makes

beam spreads of 15 to 180 degrees ble

possi-Light-emitting diodes always produce row-band (=monochromatic) radiation Thedominant wavelength and thus the colour

nar-of the light emitted – red, green, yellow orblue – is determined by the semiconductormaterial used

White LEDs and colour rendering

White LED light can be produced by ous manufacturing methods The methodthat is most widely used at present isbased on the luminescence conversionprinciple used for fluorescent lamps: a verythin film of yellow phosphor material is ap-plied to a blue LED chip, which changespart of its blue light into white To achievethe light colour required, the concentrationand chemical composition of the phosphor

vari-LED Special: The vari-LED Light Source

The advent of the LED brings a totally new light fitting onto the market In contrast to conventional lamps, LEDs are electrical components – tiny electronic chips of semiconductor crystals.

[27] LEDs do not require colour filters The

colour tone of the light is determined by the

semiconductor material used and the

domi-nant wavelength

[28] White light is generally produced by

luminescence conversion: a very thin layer of

yellow phosphor material is applied to a blue

LED chip and turns the blue light it emits into

white light

[29] LED luminous efficacy is rising Values

of 200 lumen/watt are already achieved in

material needs to be very precisely

con-trolled Today, a variety of white tones are

possible, from warm white (colour

tempera-ture  2,700 kelvin, K) through neutral

white (3,300 K) to daylight white (5,300

K) Other advantages of this method

in-clude relatively high luminous fluxes and

good colour rendering up to Ra 90

White LED light can also be produced by

additive colour mixing, i.e using

multi-LEDs or coloured LED modules to mix

coloured light of different wavelengths (red,

green and blue) This method has the

ad-vantage of permitting controlled changes of

light colour, allowing not just white but also

coloured light to be produced So RGB

so-lutions are good for dynamic coloured

light-ing applications Realislight-ing white light by

this method also calls for a great deal of

expertise because precise control is difficult

to achieve with coloured LEDs of differentbrightness and results in white light with apoorer colour rendering property – Ra 70

to 80 – than that produced by cence conversion

lumines-Where white light is required to permit aswitch from warm white to cool white foroffice applications, for example, new tech-nologies combine coloured chips withwhite LEDs The result is dynamicallychanging white light with a good colourrendering property

Efficiency and luminous efficacy

LEDs are extremely efficient light sources

The first LED, produced in 1962, achieved

a luminous efficacy of 0.1 lumen/watt(lm/W) Today, ratings in the region of 50l/W are standard and high-power LEDsreach an average of 90 lm/W By compari-son, incandescent lamps achieve around

10 lm/W, halogen lamps around 20 lm/W

And development continues apace: someLED chips already deliver 200 lm/W

However, such efficiency is achieved only

in the laboratory; in practical operation –mounted on a board and integrated in a

Colours straight from the semiconductor

LEDs do not require colour filters: their light comes

in different colours produced directly by differentsemiconductor materials Secondary colours arealso possible The major semiconductors are:

Semiconductor Abbre- Colour(s) material viation

Indium gallium green,

(white)Aluminium indium red, gallium phosphide AlInGaP orange,

yellow

gallium arsenide AlGaAsGallium arsenide red, phosphide GaASP orange,

yellow

LEDs are based on compound semiconductors.Very little energy is needed to induce them to emitlight Light-emitting diodes consist of a n-typebase semiconductor with a surplus of electrons.This is “doped” with a thin layer of p type semi-conductor material that has a deficit of electrons,called “holes” When current is applied, thesurplus electrons and “holes” migrate towards oneanother and recombine in what is known as the p-

n junction or depletion layer The energy thusreleased is converted into radiation in the semi-conductor crystal

To simplify the electrical contacts and protect theLED from environmental influences, it is encased

in a housing Reflectors ensure that the light ates upwards at angles up to 180° The light isdirected by lenses

white

light

conversion layer

LED-wire bond

How LEDs work

© licht.de

luminaire – the LEDs cannot match thatlevel of performance LED manufacturers’

data sheet specifications are based onideal laboratory conditions and extrapola-tions for the raw LED chip The values donot correspond to the actual luminous flux

of an operational LED luminaire or retrofitlamp What matters in practice is the effi-ciency of the entire LED system, i.e theway LED chips, optics and operating de-vices interact (see also page 57)

Extremely long life

LEDs have an extremely long service life

While an incandescent lamp burns foraround 1,000 hours and a fluorescent lampfor around 18,000 hours, high-performanceLEDs have a life of 50,000 hours or more

This means that an LED luminaire in tion for 11 hours a day, 250 days a year,will last for around 18 years

opera-However, the length of an LED’s life depends very much on operating and ambient tem-perature The colder the location, the moreefficiently LEDs work They do not like highambient temperatures; their luminous fluxdiminishes and their life can be significantlyshortened So effective heat dissipation is aparticularly important consideration in thedevelopment of efficient LED systems

Unlike conventional lamps, LEDs practicallynever fail However, the intensity of their

light decreases over time as a result of creasing imperfections in the semiconduc-tor crystal This characteristic is known asdegradation and means that the end of thelife of LEDs needs to be defined for a par-ticular application It is normally reachedwhen the luminous flux emitted by theLEDs decreases to 70 percent (or 50 per-cent) of the original luminous flux (see Fig.31)

in-Because of their longevity, LEDs are ally maintenance-free in practice There is

virtu-no need for lamp replacement or servicingoperations

Luminous flux and brightness

Light-emitting diodes have an exponentiallyincreasing current-voltage characteristic,i.e minor fluctuations in voltage causemajor changes in current So LED chipsneed to be operated on constant current.They should not be connected directly to avoltage source The more power a diodeconsumes, the brighter it shines The catch

is that higher operating currents heat thesemiconductor – and thus reduce effi-ciency So high-intensity LEDs need goodthermal management to remove the heatfrom the LED chip Thanks to larger LEDchips and new designs for optimal heatdissipation, modern high-power LEDs (1W– 5W) can be operated on higher currentsabove 100 milliampere (mA) They emit a

[31] LEDs do not fail but the intensity of

the light they produce diminishes over time

The lifespan (L) of an LED thus needs to be

defined for different applications For

emer-gency lighting, for example, ratings up to L80

or more are required; this means that the

LED reaches the end of its service life when

the luminous flux falls to 80 percent of the

original flux measured For general lighting,

values of L50 or L70 are defined The

lifes-pan of an LED depends to a large extent on

ambient and operating temperature Where

an LED is operated at a high temperature

(Tc1) or with poor thermal management, its

life is shortened

[32] Highly flexible LED module in SMD

1907… English experimenter Henry Joseph Round

discovers that inorganic substances can emit light

when an electric current is passed through them He

reports his findings the very same year in the journal

“Electrical World” However, because his primary

focus is the development of a new radiolocation

process for shipping, his discovery initially sinks into

oblivion

1921… The Russian physicist Oleg Vladimirovich

Losev observes electroluminescence again Because

he believes it to be the converse of Einstein’s

photo-electric effect, he studies the phenomenon more

closely through to 1942

1935… George Destriau reports on light produced

by passing an electric current through zinc sulphide

powders and calls it “Losev light” in honour of the

Russian physicist

1951… The development of the transistor brings

a scientific breakthrough for semiconductor physics

The emission of light can now also be explained

At first, scientists keep on experimenting with zincsulphide It is not until 1959 that light generationresearch focuses on semiconductors; particularlyimportant here is the visible light emission produced

by a mixed crystal of gallium arsenide (GaAs) andgallium phosphide (GaP)

1962… The first red luminescent diode (GaAsP)appears on the market, developed by the Americanscientist Nick Holonyak It marks the birth of industri-ally manufactured LEDs

1971… Owing to the development of new improvedsemiconductor materials, light-emitting diodes arenow also available in other colours: green, orange,yellow At the same time, steady progress is made onimproving LED performance and efficiency

1980s through to the early 1990s … The new semiconductor material gallium nitride (GaN) permitsgreen tones through to ultraviolet and paves the

History of the LED:

A long road to market

way, in 1993, for Shuji Nakamura’s invention of thefirst commercially successful brilliant blue LED inJapan Blue LEDs prior to that were based on theindirect semiconductor silicon carbide, which is notvery efficient As well as the blue GaN LED, Naka-mura develops the very efficient green indiumgallium nitride diode (InGaN-LED) and later also awhite LED

1995… The first LED using phosphor material toproduce white light by luminescence conversion ispresented Two years later, these white light-emittingdiodes are on the market

2006… The first 100 lm/W LEDs are available Interms of efficiency, they are surpassed only by gasdischarge lamps

In the recent past, the efficiency of LEDs hasdoubled every two years They are conquering moreand more applications and their development shows

no signs of coming to a halt …

great deal more light than earlier versions

and are already breaking records in terms

of luminous efficacy: up to 200 lumen on

1A operating current Simple standard

LEDs, by comparison, deliver 1-2 lumen

from 20 mA

Low-power LEDs

Low-power LEDs – also referred to as

ra-dial LEDs – include the classical 3 or 5 mm

designs, usually with two “legs” and a

nar-row beam spread of 15° to 30° The 5 mm

LED launched the triumphant career of

the light-emitting diode; today,

high-per-form ance diodes are in much more

wide-spread use Low power LEDs operate on

currents from 20 mA to a maximum of

100 mA

Superflux or high flux LEDs (also called

spi-der or piranha LEDs) have four pins They

generally operate on 70 mA and have a

higher light output The housing of these

LEDs can also accommodate several

chips, which can be separately controlled

Their design permits a wider beam spread

of 90° to 130° Superflux LEDs are used

mostly in automotive engineering

High-power LEDs

High-power LEDs – also referred to ashigh-performance LEDs – deliver the

most light of all They initially

came onto the

market as efficient 1W ages operated at 350 mA Shortly after-wards, 3W and 5W high-power LEDs ap-peared on the scene At the same time,LEDs were further miniaturised The small-est high-power LED available is little largerthan a matchstick head and achieves 100lumen/watt efficiency

pack-Types of LED

Wired LEDs(radial LEDs) date back to theearly days of LED technology The internalLED chip is encased in a plastic housingthat protects it from damage Today, be-cause of their generally low light output,these low-power LEDs are predominantlyused for simple signal indicators

32

COB LEDs(= chip onboard) are used for tightlypacked high-power LED modules

With COB technology, the LED chipsare placed directly on a printed-circuitboard (PCB) and wire-bonded tothe contact surface An

epoxy lens, or

“bubble”, defines the beamspread, which can be narrow or wide-an-gled

SMD LEDs(= surface mounted devices)are very small mass-produced products.They are placed directly on a PCB andelectrically contacted by soldering Likewired LEDs, they are encapsulated SMDLEDs are the type most widely used inmodules or luminaires

SMD models are fitted both with low-powerLEDs and with high-power LEDs They permit the industrial production of high-per-formance modules of extremely shallowand narrow construction

[33] LEDs are generally used as modules,

which are either custom-designed or

stan-dardised These modules offer optimal scope

for fine-tuning to the relevant application and

can be used directly as encapsulated

mod-ules even without a luminaire housing The

two LED retrofit lamps on the right replace

incandescent lamps with a screw base (top)

and halogen reflector lamps with a pin base

(bottom)

The tiny semiconductor diode has sented a new light source for lighting: theLED module Basically, it consists of one ormore light-emitting diodes mounted on aPCB The PCB provides the electrical con-nection for the diodes, dissipates heat andenables the LEDs to be controlled The flatmodules permit flexible and efficient use ofLED technology They are fitted with differ-ent types of LED, depending on application

pre-LED modules

LED modules are a versatile light sourcepermitting totally new design solutions Asencapsulated modules, they require nohousing and can be directly recessed, forinstance, in floor or ceiling ducts As indi-vidual modules, they are integrated in mini-malist LED luminaires and, with an appro-

priate base, serve as replacements formany conventional lamps

Linear LED modulesare particularly suitablefor wallwashing effects and for architecturallighting They give depth to facades and arches and fit into narrow outlet ducting They can also be used to realise long lines of light

Flexible LED modulesare particularly good

at negotiating curves and corners They aremostly fitted with SMD LEDs The flat mod-ules are the right solution where curved sur-faces need to be illuminated or back-lit, e.g.lettering or handrails

Planar LED modulesare normally available

as ready-to-use LED panels with diffuseglass or plastic surfaces They are used aslight tiles or complete luminous ceilings

LED Special:

Modules, Systems – and Quality Features

Light-emitting diodes can only be used for lighting tasks when assembled as a module on a printed circuit

board (PCB) The production of high-performance modules, lamps and complete LED luminaires calls for special manufacturing processes and a great deal of technological expertise is needed to meet the relevant quality

requirements

33

Where a number of modules are connected

– and an appropriate control system

in-stalled – large-area displays can be realised

LED chainsare used where surfaces need

to be back-lit or under-lit, e.g in light

adver-tising

Retrofit lamps: LEDs with base

LEDs with pin or screw base are a special

module variant With an E14 or E27 screw

base and a classical “bulb” design, they

re-place conventional incandescent lamps;

with pin bases, they replace the

correspon-ding halogen lamps Delivering warm white

or coloured light, retrofit LED lamps are an

energy-saving alternative for home or small

office use They can simply be inserted into

existing luminaires However, they do not

match the performance of a complete LED

luminaire Even so, they are a good

alterna-tive: an 8W warm white LED light bulb, for

example, has a life of around 25,000

oper-ating hours – which is nearly 25 years at

almost three hours a day

LED luminaires and LED systems

One of the prime requirements for an

effi-cient LED solution is optimal

synchroniza-tion of module and luminaire housing; thetwo always form a complete system Theirproduction calls not only for a great deal ofdevelopment and manufacturing expertisebut also for the use of high-grade materi-als Among the distinguishing features of aquality luminaire are good – and compact –solutions for lighting control, thermal man-agement and optical design

LED luminaires or LED systems for cessed and surface-mounted fittings arealways made in four stages (see Fig 34):

re-Their manufacture starts with an LED chip,which is encased in plastic to protect itfrom environmental influences and defineits emittance characteristics and thenplaced in a housing

This diode (stage 2) is mounted on a PCB,which provides the electronics, control andthermal management In the third stage,the LED-PCB is then fitted with secondaryoptics such as lenses, reflectors or dif-fusers

In stage 4, the LED module is integrated

in the LED luminaire In this productionphase, a great deal of attention is paid tothe rear of the luminaire, where thermalmanagement is a major issue This ensures

[34] The production of efficient LED tems calls for a great deal of technologicalexpertise The quality of the components andthe standard of manufacturing are crucial forthe efficiency and performance of an LED luminaire

sys-34

that heat is conducted away from thediode and is crucial for the efficiency andlifespan of the system as a whole

Quality features and maintenance factor

LEDs are in vogue – and the market is

flood-ed with products that do not always meetthe necessary requirements In many cases,poor systems do not reveal their weaknessuntil they are in operation Quality products

> offer balanced luminance that cannotharm the human eye,

> have minimal early failures (approx twoper million LEDs) and carry a manufac-turer’s warranty,

> offer the prospect of future replacement

in the same lighting quality despite the rapiddevelopment of LED technology,

> feature good thermal management, suring that luminaires do not get too hotand can be touched without risk,

en-> offer a good maintenance factor

The maintenance factor (MF) of a lighting stallation is the ratio of the luminous flux atthe time of maintenance to the original lumi-nous flux when the system is installed Ittakes account of

in-> the reduction of luminous flux due to thefailure and ageing of lamps,

> the possible soiling of a luminaire in thecourse of time,

> room or outdoor conditions that maycontribute to soiling and ageing

For example: Where MF = 0.5, a lighting stallation needs to produce twice as muchluminous flux at the outset so that it will stillprovide the illuminance required for standardcompliance by the end of the first mainte-nance interval Generally speaking, the qual-ity of LED luminaires is reflected in uniformlight colours and homogeneous brightness

in-as well in-as in the rated life of the system in-as awhole Important issues in this context arethermal management and binning

[35] Agreeably uniform, glare-free light is

provided in the office by the extremely flat

suspended task area luminaire with

direct/in-direct light distribution and integrated lighting

management system Another advantage is

its long life, which saves maintenance costs

35

Thermal management

Even though the light radiated by an LED is

not hot, it is wrong to assume that LEDs

do not give off heat Just like other lamps,

LEDs convert only part of the incoming

en-ergy into light – the rest generates heat

in-side the semiconductor To ensure a long

life and high efficiency, it is imperative that

this heat should be transferred This applies

particularly to high luminous flux LEDs

Reliable manufacturers thus always quote

an LED ambient temperature in which the

luminous flux and lifespan of their luminaires

and modules are reached

Binning

In the industrial production of LEDs, there

are always differences within batches:

diodes vary, for example, in their colour

and luminous intensity To guarantee

con-stant lighting quality with the same ness level and uniform light colour, LEDsneed to be sorted within each batch This

bright-is called binning Major selection criteriahere are:

> luminous flux, measured in lumens (lm)

> colour temperature, measured in vins (K)

kel-> forward voltage, measured in volts (V)

[36] ] Uniform LED light colours are guaranteed by ANSI binning

The colours of LEDs are subject to natural fluctuations To guarantee a uniformlight colour, they need to be categorised The process of sorting LEDs by colour isknown as binning

The red triangle in the chromaticity diagram (left) of the International LightingCommission CIE indicates the space in which a chromatic locus could theoreti-cally be plotted by mixing the colours of three LEDs If the binning group is on theblack curve of the Planckian locus, it is classed as “pure white” If the bin is abovethe line, the LED has a greenish tint

Today, LEDs are sorted on the basis of the ANSI bin standard (ANSI = AmericanNational Standards Institute) This defines colour variations in xy space with thehelp of a MacAdam ellipse and recommends that colour values should be within

an ellipse with four threshold units LEDs in these tightly defined bins guaranteeuniform light colours, e.g 2,700 K for warm white

© licht.de

Lighting plays an important role in hotels,restaurants and wellness centres It con-tributes crucially to a guest’s sense of well-being and desire to return Here, light playsout its emotional qualities, underlining acomfortable and agreeable atmosphere

At the same time, lighting facilitates tion, e.g on parking decks, in corridors andpassageways In conference rooms, hotelrooms and service areas, lighting alsoneeds to cater for different room uses –while keeping costs as low as possible

orienta-High-power LED systems meet the plex requirements of restaurants and hospi-tality venues at the highest level: They

com-> can be flexibly controlled and offer namic scene-setting lighting in rich colours,

dy-> provide different white tones to underline

a homely or fresh ambience,

> have a service life of 50,000 hours ormore,

> are very efficient,

> are small and discreet and accentuate chitecture,

ar-> save maintenance costs and have a lowenvironmental impact

The tiny power packs not only ensure rate lighting quality; they are also extremelyeconomical on energy LED solutions andintelligent lighting control can cut lightingcosts by as much as 75 percent Another

first-LEDs for Hotels and Hospitality

From traditional hotel to trendy bistro, country inn to wellness oasis – successful “hosts” cosset their customers, offering pleasure and wellbeing The right light is just as important here as impeccable service

37

advantage: their longevity saves

mainte-nance costs by eliminating the need for

fre-quent lamp replacement in difficult places

like high stairwells What is more, the low

heat gain of LEDs reduces air-conditioning

costs

First impressions count

With a broad spectrum of colours and

colour temperatures, LEDs ensure a friendly

reception They provide guidance for

visi-tors and facilitate communication between

guests and staff Planar light conveys

gen-erosity and makes for good general lighting

Such solutions can be realised with flooding

LED light from cornices or with a full diffuse

opal “skylight ceiling” of back-lit glass

Warm white light or cheerful bright colour

tones are the most suitable options

Walk-over recessed floor lights or discreet

light panels in the wall guide the visitor to

the reception There, the glare free warm

white light of elegant LED luminaires

facili-tates work at the computer Good colour

rendering with Ra 90 guarantees that

colours, faces and objects look natural

In lobby, bar and corridor, directional LED

spots set striking accents as

energy-effi-cient replacements for halogen lamps Their

big advantage: they emit neither ultraviolet

nor infrared light So even old masters

sus-tain no damage and eye-catching creations

on the dessert buffet are cast in an

appetis-ing light with no risk of them dryappetis-ing out

Colour and dynamism for

lighting comfort

Coloured lighting for selected surfaces and

dynamic light hold a special fascination

Experienced hoteliers are not the only ones

[37] The slate wall is an eye-catcher in the

lounge, lent depth by cubic recessed

lumi-naires with single 1.2W LEDs radiating light in

three different white tones

[38] The right lighting helps us unwind

Here, a homogeneous “light wall” provides

agreeably diffuse light at the bed 38

40

who realise this; the positive impact on

human beings has been confirmed by

nu-merous studies With LED solutions, it is

particularly easy to harness the beneficial

effects of colour and dynamic light And

there is no need for colour filters: given an

appropriate module, a single LED luminaire

can produce more than 16 million different

colours as well as a range of white tones

LED lighting with dynamic colour

manage-ment has various uses In a hotel room, it

enables the guest to set “his” lighting to

suit his biorhythms – fresh white tones with

a high blue content in the morning to help

him wake up, more red content in the

evening to help him unwind In conference

rooms, the lighting can be switched as

required from concentration-boosting white

tones through gently soothing mood light

to inspiring colour changes for creative

brainstorming

Intelligent, sensitive colour management

also makes for great effects in wellness

centres – effects that customers appreciate

Green tones are soothing for a relaxingmassage, a delicate violet is good for therest zone of the sauna and turquoise blueconveys a sense of cleanliness and fresh-ness in the whirlpool To ensure safety inswimming pools, plunge pools and show-ers, however, any LED luminaires usedthere need to be designed to appropriatedegrees of protection

High-quality LED systems can be infinitelydimmed They can thus provide subduedlighting for guests in rest zones and brightlight for cleaning

Video-capable LED systems add a highlight

to lounge and bar areas They let ceilings tell stories Programmed to create differentshapes and slowly changing colours, theymake for a subtle cosy atmosphere; loadedwith images, they set trends The planar lu-minaires can be installed on ceilings or walls

Lighting management for comfort

Tailoring lighting to preferences and needs

calls for lighting control and appropriatemanagement systems They should be easy

to use and convenient for guests and staff.Simple control is offered by multifunctionaloperator interfaces where a single panel re-places a cluster of switches and dimmers

Clearly identified programmed lighting mospheres can be activated at the push

at-of a button or by remote control – a come convenience in any hotel or confer-ence room At the same time, lighting andblinds can be adjusted to suit daylight and weather Where time of day and humanpresence are taken into account, lightingmanagement permits a further sustainablereduction of energy consumption This alsomakes good financial sense in toilet facilitiesand on parking decks

wel-Long-life low-consumption LED luminairescombined with lighting management thusmeet the requirements for efficient, top-quality lighting for every part of a building.Depending on configuration, all areas can

be centrally monitored and controlled –from hotel room to car park

[39] Downlights and cornice lighting over

the entrance mark the route to the reception

[40] LEDs create an attractive lighting

at-mosphere in the restaurant: the back-lit

counter is a prominent design feature

Slim-line LED modules also set the scene for

glasses on the shelves on the rear wall

[41] LED solutions with dynamic colour

management are a good choice for wellness

facilities They pamper guests with

stimulat-ing or relaxstimulat-ing light, dependstimulat-ing on the time

42